First thing - I'd like to reassure you that we will never locked you out of your account. You will always have access to your passwords, even if your account becomes frozen. You will still be able to view all of your items and copy your passwords. There are restrictions on frozen account which mean you won't be able to add new items to vaults, edit items, invite people to your family or team, or autofill items in your browser until the account becomes unfrozen.
As another commenter here mentioned, there are a number of potential points that can cause a payment failure like this. The absolute quickest approach to resolve this would be to try using a different payment method. I know that isn't ideal.
As for the current payment method problem, can you please respond back to our support team and mention that I reached out to you here? It will help me to connect some dots and look into your issue specifically, and we can communicate through more official channels.
Thanks, Erik